UV-B filters

ABSTRACT

Disclosed is a 2-phenyl-benzimidazolesulfonic acid according to the formula  
                 
 
     in which  
     n is 0, 1 or 2 and  
     m is 2 or 3,  
     R1, R2, R3, R4 and R5, are each a radical such as H, C 1-8 -alkyl, C 1-8 -alkoxy, hydroxyl, sulfate, nitro, F, Cl, Br or I radicals, and  
     R6 is a C 1-8 -alkyl or C 1-8 -alkoxy radical.  
     This compound can be effectively used as a UV filter, and as part of a cosmetic formulation which comprise these compounds. A process for preparation of the compound is disclosed as well.

[0001] The present invention relates to a 2-phenyl-benzimidazolesulfonicacids, to the use thereof as a UV filter, to cosmetic preparations whichcomprise these compounds, and to a preparation process for thecompounds.

[0002] A suntan of the skin to whatever degree is regarded in today'ssociety as attractive and as an expression of vigor and health. As wellas this desired effect of the sun on the skin, however, a number ofundesired secondary effects arise, such as sunburn or premature skinaging and the development of wrinkles. A number of performance UVfilters have been developed which, applied to the skin in the form ofcreams, lotions or gels, can effectively delay the development ofsunburn even when the incidence of solar rays is relatively high.

[0003] The UV filter present in the pharmaceutical or cosmeticformulation forms a film or a layer on the surface of the skin and doesnot penetrate into deeper skin layers with other substances present inthe formulation. Known UV filters or sun protection agents thus act onlyby absorbing certain regions of sunlight; meaning that this radiationcannot penetrate into deeper layers of the skin.

[0004] As is known, the most hazardous part of solar radiation is formedby the ultraviolet rays having a wavelength of less than 400 nm. Thelower limit of the ultraviolet rays which reach the surface of the earthis limited by the absorption in the ozone layer to about 280 nm orabove. The sun protection filters which are currently customary incosmetics absorb in a wavelength range from 280 to 400 nm. This rangeincludes UV-B rays having a wavelength between 280 and 320 nm, whichplay a decisive role in the formation of a solar erythema, and UV-Arays, having a wavelength between 320 and 400 nm, which tan the skin butalso age it, and favor the triggering of an erythematous reaction or canexacerbate this reaction in certain people or even trigger phototoxic orphotoallergic and irritative reactions.

[0005] The object of skin care cosmetics is to obtain the impression ofa youthful skin. In principle, there are various ways of achieving thisobject. For example, existing skin damage, such as irregularpigmentation or the development of wrinkles can be smoothed out bycovering powders or creams. Another approach is to protect the skinagainst environmental influences which lead to permanent damage and thusaging of the skin.

[0006] The idea is therefore to intervene in a preventative manner andthus to delay the aging process. One example of this is the UV filtersalready mentioned which, as a result of absorption of certain wavelengthregions, prevent or at least reduce skin damage. Depending on theposition of their absorption maxima, UV absorbers for cosmetic anddermatological preparations are divided into UV-A and UV-B absorbers.UV-A absorbers usually also absorb in the UV-B region and are thusalternatively referred to as broad-band absorbers or broad-band filters.However, particularly in avoiding skin damage as a result of theformation of solar erythemas, the UV-B filters are of particularimportance, since formulations based on broad-band filters alone offerinadequate protection or prevent entirely the desired tanning of theskin. For this reason, there is a continuous need for substances havingan absorption maximum in the UV-B region which can be incorporatedeasily into cosmetic formulations.

[0007] Of decisive importance for the formulation is the solubility ofthe filter substances in the oil and water phases since it is necessary,particularly for establishing a high protection factor, to incorporatefilters into all phases of a formulation. The oil-soluble UV-B filtersinclude isooctyl methoxycinnamate, isoamyl methoxycinnamate andmethylbenzylidenecamphor. Examples of water-soluble UV filters are, inparticular, the salts of 2-phenylbenzimidazole-5-sulfonic acid, the useof which as UV ray filter has already been described in GermanReichspatent No. 676 103.

[0008] However, a disadvantage of these water-soluble UV-B filters isthat formulation is only possible in an alkaline medium since thesulfonic acid precipitates out at a pH below 7.

[0009] There is thus also a need for water-soluble UV-B filters whichare highly suitable for the formulation of cosmetic formulations.

[0010] It has now surprisingly been found that certain2-phenylbenzimidazolesulfonic acids and salts thereof can be readilyincorporated into cosmetic formulations, while avoiding theabove-mentioned problems.

[0011] The present invention accordingly firstly provides2-phenylbenzimidazolesulfonic acids of the formula I

[0012] in which n is 0, 1 or 2 and m is 2 or 3. R1, R2, R3, R4 and R5are each a radical from the group H, C₁₋₈-alkyl, C₁₋₈-alkoxy, hydroxyl,sulfate, nitro, F, Cl, Br or I radicals, and R6 is a C₁₋₁₈-alkyl orC-₁₋₈-alkoxy radical.

[0013] For the purposes of the present invention,2-phenyl-benzimidazolesulfonic acids are here in principle alsounderstood as meaning the salts of these acids. The salts are preferablythe alkali metal salts, and in particular the sodium or potassium salts,or the ammonium salts, in particular the triethanolammonium salts of thecorresponding sulfonic acids.

[0014] In a preferred 2-phenylbenzimidazolesulfonic acid according toformula I, m=2 and n=0 or n=1, preferably at least 4 radicals from thegroup R1, R2, R3, R4 and R5 are H, and particularly preferably even allradicals R1-R5 are H. According to the invention, particular preferenceis accordingly given to 2-phenylbenzimidiazole-4,6-disulfonic acidwhich, as shown in formula Ia, is usually in betaine form.

[0015] The 2-phenylbenzimidazolesulfonic acid according to the inventioncan be obtained by any desired preparation process suitable for thispurpose. Processes which have proven particularly suitable andeconomical are those in which an ortho-phenylenediamine or a derivativethereof is reacted with an arylcarboxylic acid or an arylcarboxylic acidderivative.

[0016] The present invention thus secondly provides a process for thepreparation of the abovedescribed 2-phenylbenzimidazolesulfonic acids,in which an o-phenylenediamine according to formula II

[0017] is reacted with a second compound according to formula III

[0018] where R1, R2, R3, R4 and R5, in each case independently of oneanother, are a radical from the group of H, C₁₋₈-alkyl, C-₁₋₈-alkoxy,hydroxyl, nitro, F, Cl, Br or I radicals, and X is chosen from theradicals —COOH, —COCl, —COBr, —CN or —COOR, where R is a C₁₋₂₀-alkylradical.

[0019] In a preferred embodiment of the process, sulfuric acid, inparticular 96% sulfuric acid, is used as solvent. Here, even thesulfuric acid on its own effects sulfonation of the benzimidazole at asuitable temperature. Thus, international application WO 93/15061 hasalready described a process in which monosulfonated products areobtained by reaction in sulfuric acid.

[0020] However, in the process for the preparation of polysulfonatedbenzimidazoles, it is preferred if an activated sulfuric acid is used,activation preferably being carried out by chlorosulfonic acid or sulfurtrioxide. Sulfuric acid alone typically is not strong enough to act as areagent for this process because it is believed that water forms duringthe reaction and dilutes the sulfuric acid. Activation of the acidimproved the reactivity of the acid in the process.

[0021] The use of chlorosulfonic acid for the preparation ofbisbenzimidazoloylsulfonic acids has already been described in Europeanpatent application EP-A-669 323.

[0022] However, there are no indications that it is also possible to usechlorosulfonic acid to prepare the compounds according to the inventionin the specification.

[0023] If the activation is carried out using sulfur trioxide, use ispreferably made of the “fuming” sulfuric acid called oleum, which is asolution of sulfur trioxide in concentrated sulfuric acid. The use ofsulfur trioxide (oleum) for the activation of the sulfuric acid hasvarious advantages compared with the use of chlorosulfonic acid:

[0024] gas (HCl) is not evolved during the reaction, meaning thatpressure regulation is not necessary,

[0025] accordingly, the collection and disposal of the aggressive gas(HCl) is not required,

[0026] while extremely corrosion-resistant apparatuses are required forthe chloride-containing sulfuric acid which is formed if chlorosulfonicacid is used, the process with oleum can be carried out in less complexequipment,

[0027] after hydrolysis of the oleum, sulfuric acid is present which canbe recycled, with relative ease while the recycling of thechloride-containing sulfuric acid resulting from the use ofchlorosulfonic acid is only possible with difficulty.

[0028] As a result of these advantages, it is preferred according to thepresent invention to activate the sulfuric acid using sulfur trioxide(oleum).

[0029] If the process according to the invention is carried out withactivated sulfuric acid, then it is preferred that X in the secondcompound of formula III is a radical —COOH, i.e., that formula III is anarylcarboxylic acid. In another likewise preferred embodiment of theprocess, X in formula III is a radical —COOR, where R is a C₁₋₂₀-alkylradical, preferably a C₁₋₈-alkyl radical and particularly preferably amethyl or ethyl radical.

[0030] Here, it is particularly preferred that the reaction is carriedout at temperatures between 20° C. and 200° C., preferably between 160°C. and 190° C. The reaction temperature is usually maintained for 2 to 8hours. At reaction times of less than 2 hours, monosulfonation productsare still observed, which can only be separated off from the productwith difficulty.

[0031] Implementation of the process according to the invention is initself straightforward for one skilled in the art. A preferredembodiment for carrying out the reaction is given below. This may serveas an example, but does not limit the possible embodiments for carryingout the reaction:

[0032] The sulfuric acid, preferably in the form of a 50-100% solution,and in particular as a concentrated approximately 96% solution, isintroduced. The ortho-phenylenediamine, or derivative thereof, isintroduced. Activation with oleum (e.g. a 65% solution of sulfurtrioxide in sulfuric acid) is then carried out at a temperaturepreferably below 150° C. The amount of sulfur trioxide is chosen suchthat all of the water liberated during the reaction can be collected.For example, for the preparation of a benzimidazole-disulfonic acid, atleast 4 mol of sulfur trioxide are used per mole of o-phenylenediamine.

[0033] The addition of the second reactant (arylcarboxylic acid orarylcarboxylic acid derivative) is preferably only carried out forsafety reasons after cooling to a temperature below 100° C. since thetemperature of the reaction mixture may increase further as the resultof the addition. The arylcarboxylic acid is expediently used in theratio 1:1 to the phenylenediamine to obtain products according to theinvention.

[0034] The reaction mixture is slowly heated to temperatures between 150and 250° C., preferably between 160 and 200° C. and maintained at thistemperature for 2 to 8 hours, optionally with stirring. The reactionmixture is then cooled, preferably to temperatures below 10° C., andhydrolyzed in water.

[0035] After the mixture has been stirred briefly, preferably 20 minutesto 2 hours, the solid constituents are separated off, preferably washedwith warm water and dried.

[0036] To purify the dried crude product, it is preferably dissolved insodium hydroxide solution, and the resulting solution is purified,preferably with activated carbon. The end-product is precipitated out ofthe colorless solution using an acid, preferably a mineral acid; forexample sulphuric acid.

[0037] Because of its absorption maxima in the UV-B region, the2-phenylbenzimidazolesulfonic acid according to the invention issuitable as a UV-B filter substance.

[0038] Accordingly, the present invention further provides for the useof a 2-phenylbenzimidazolesulfonic acid as a UV filter, in particular asa UV-B filter.

[0039] Because of this use option, the substances according to theinvention are highly suitable for use in cosmetic formulations. Theinvention thus further relates to cosmetic formulations having UVprotection properties which comprise at least one compound of formula Iaccording to the invention.

[0040] The protective action of these formulations against UV radiationcan be improved if the formulation comprises one or more additional UVfilter substances in addition to the UV filter according to theinvention.

[0041] In principle, it appears that all UV filters are suitable forcombination with the filter substance herein. Particular preference isgiven to combination with those UV filters whose physiological safetyhas already been demonstrated. There are many tried and testedsubstances known from the specialist literature both for UVA and alsoUVB filters, such as:

[0042] benzylidenecamphor derivatives, such as3-(4′-methylbenzylidene)-dl-camphor (e.g. Eusolex® 6300),3-benzylidenecamphor (e.g. Mexoryl® SD), polymers of N-{(2 and4)-[(2-oxoborn-3-ylidene)-methyl]benzyl}acrylamide (e.g. Mexoryl® SW),N,N,N,-trimethyl-4-(2-oxoborn-3-ylidenemethyl)-anilinium methylsulfate-(e.g. Mexoryl® SK) or α-(2-oxoborn-3-ylidene)toluene-4-sulfonic acid(e.g. Mexoryl® SL),

[0043] benzoylmethanes or dibenzoylmethanes, such as1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione (e.g.Eusolex® 9020) or 4-isopropyldibenzoylmethane,

[0044] benzophenones, such as 2-hydroxy-4-methoxybenzophenone (e.g.Eusolex® 4360) or 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid andits sodium salt (e.g. Uvinul® MS-40),

[0045] methoxycinnamic esters, such as octyl methoxycinnamate (e.g.Eusolex® 2292), isopentyl 4-methoxycinnamate, e.g. as a mixture of theisomers (e.g. Neo Heliopan® E 1000),

[0046] salicylate derivatives, such as 2-ethylhexyl salicylate (e.g.Eusolex® OS), 4-isopropylbenzyl salicylate (e.g. Megasol®) or3,3,5-trimethylcyclohexyl salicylate (e.g. Eusolex® HMS),

[0047] 4-aminobenzoic acid and derivatives, such as 4-aminobenzoic acid,2-ethylhexyl 4-(dimethyl-amino)benzoate (e.g. Eusolex® 6007),ethoxylated ethyl 4-aminobenzoate (e.g. Uvinul® P25),

[0048] benzimidazole derivatives, such as2-phenylbenzimidazole-5-sulfonic acid, and its potassium, sodium,lithium, ammonium and triethanolamine salts (e.g. Eusolex® 232),2,2′-(1,4-phenylene)bis(1H-benzimidazole-4,6-disulfonic acid, monosodiumsalt) (CAS No. 180 898-37-7) and2,2′-(1,4-phenylene)bis(1H-benzimidazole-5-sulfonic acid) and itspotassium, sodium and triethanolamine salts

[0049] and further substances, such as 2-ethylhexyl2-cyano-3,3-diphenylacrylate (e.g. Eusolex® OCR),3,3-(1,4-phenylenedimethylene)bis(7,7-dimethyl-2-oxobicyclo-[2.2.1]hept-1-ylmethanesulfonicacid, and its salts (e.g. Mexoryl® SX),2,4,6-trianilino-(p-carbo-2′-ethylhexyl-1′-oxy)-1,3,5-triazine (e.g.Uvinul® T 150),2-(2H-benzo-triazole-2-yl)-4-methyl-6-(2-methyl-3-(1,3,3,3-tetramethyl-1-(trimethylsilyloxy)disiloxanyl)-propyl)phenol(e.g. Silatriazole®),4,4′-[(6-[4-((1,1,-dimethylethyl)aminocarbonyl)phenylamino]-1,3,5-triazine-2,4-diyl)diimino]bis(benzoicacid 2-ethylhexyl ester) (e.g. Uvasorb® HEB),α-trimethylsilyl)-ω-[trimethylsilyl)oxy]poly[oxy-(dimethyl [andapproximately 6%methyl[2-[p-[2,2-bis(ethoxycarbonyl]vinyl]phenoxy]-1-methylene-ethyl]and about 1.5%methyl[3-[p-2,2-bis(ethoxy-carbonyl)vinyl)phenoxy)propenyl) and 0.1 to0.4% (methylhydrogen)silylene]] (n≈60) (CAS No. 207 574-74-1),2,2′-methylenebis(6-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol)(CAS No. 103 597-45-1) and 2,4-bis{[4-(2-ethylhexyloxy)-2-hydroxy]phenyl}-6-(4-methoxyphenyl)-1,3,5-triazine(CAS No. 103 597-45-[lacuna], 187 393-00-6).

[0050] The compounds given in the list are only to be regarded asexamples. It is of course also possible to use other UV filters. Theseorganic UV filters are, and the 2-phenylbenzimidazolesulfonic acidsaccording to the invention, are typically each incorporated intocosmetic formulations in an amount of from 0.5 to 20% by weight of theformulation, preferably in an amount of 1-15% by weight and particularlypreferably in an amount of from 2 to 8% by weight per individualsubstance. Overall, the organic filters usually comprise up to 40% byweight, preferably 5 to 25% by weight, of the formulation, whichincludes the filter substance of the invention and any additionalorganic filter substances.

[0051] Inorganic UV filters such as those from the group of titaniumdioxides, such as, for example, coated titanium dioxide (e.g. Eusolex®T-2000, Eusolex® T-AQUA), zinc oxides (e.g. Sachtotec®), iron oxides andalso cerium oxides can also be combined. These inorganic UV filters areusually incorporated into cosmetic formulations in an amount of from 0.5to 20 per cent by weight of the overall formulation, preferably 2-10%.

[0052] If various inorganic or organic UV filters are used, then thesecan be used in virtually any ratios relative to one another. The ratiosof the individual substances to one another are usually in the range1:10-10:1, preferably in the range 1:5-5:1 and particularly preferablyin the range 1:2-2:1. If UV-A filters are used in addition to UV-Bfilters, then it is advantageous for most applications if the proportionof UV-B filters predominates and the ratio of UV-A filters:UV-B filtersis preferably in the range 1:1 to 1:3.

[0053] Preferred filter compounds for combination with the2-phenylbenzimidazolesulfonic acids according to the invention,preferred compounds having UV-filtering properties for the cosmeticpreparations are 3-(4′-methylbenzylidine)-dl-camphor,1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione,4-isopropyldibenzoylmethane, 2-hydroxy-4-methoxybenzo-phenone, octylmethoxycinnamate, 3,3,5-trimethylcyclohexyl salicylate, 2-ethylhexyl4-(dimethyl-amino)benzoate, 2-ethylhexyl 2-cyano-3,3-diphenyl-acrylate,coated titanium dioxide and in particular2-phenylbenzimidazole-5-sulfonic acid and2,2′-(1,4-phenylene)bis(1H-benzimidazole-5-sulfonic acid) and itspotassium, sodium, lithium, ammoniium and triethanolamine salts.

[0054] The protecting action against oxidative stress or against theeffect of free radicals can be further improved if the formulationcomprises one or more antioxidants.

[0055] There are many tried and tested substances known from thespecialist literature which can be used as an antioxidant in theformulation such as amino acids (e.g. glycine, histidine, tyrosine,tryptophan) and derivatives thereof, imidazoles (e.g. urocanic acid) andderivatives thereof, peptides, such as D,L-carnosine, D-carnosine,L-carnosine and derivatives thereof (e.g. anserine), carotinoids,carotenes (e.g. α-carotene, β-carotene, lycopene) and derivativesthereof, chlorogenic acid and derivatives thereof, lipoic acid andderivatives thereof (e.g. dihydrolipoic acid), aurothioglucose,propylthiouracil and other thiols (e.g. thioredoxin, glutathione,cysteine, cystine, cystamine and the glycosyl, N-acetyl, methyl, ethyl,propyl, amyl, butyl and lauryl, palmitoyl, oleyl, γ-linoleyl,cholesteryl and glycerylesters thereof), and salts thereof, dilaurylthiodipropionate, distearyl thiodipropionate, thiodipropionic acid andderivatives thereof (esters, ethers, peptides, lipids, nucleotides,nucleosides and salts), and sulfoximine compounds (e.g.buthionine-sulfoximine, homocysteine-sulfoximine, buthionine-sulfone,penta-, hexa- and heptathionine-sulfoximine) in very low tolerated doses(e.g. pmol to μmol/kg), and also (metal) chelating agents, (e.g.α-hydroxy fatty acids, palmitic acid, phytic acid, lactoferrin),α-hydroxy acids (e.g. citric acid, lactic acid, malic acid), humic acid,bile acid, bile extracts, bilirubin, biliverdin, EDTA, EGTA andderivatives thereof, unsaturated fatty acids and derivatives thereof,vitamin C and derivatives (e.g. ascorbyl palmitate, magnesium ascorbylphosphate, ascorbyl acetate), tocopherols and derivatives (e.g. vitaminE acetate), vitamin A and derivatives (e.g. vitamin A palmitate), andconiferyl benzoate of benzoin resin, rutin and salts of the sulfuricester of rutin and derivatives thereof, α-glycosyl rutin, ferulic acid,furfurylidineglucitol, carosine, butylhydroxy-toluene,butylhydroxyanisol, nordihydroguaretic acid, trihydroxybutyrophenone,quercetin, uric acid and derivatives thereof, mannose and derivativesthereof, zinc and derivatives thereof (e.g. ZnO, ZnSO₄), selenium andderivatives thereof (e.g. selenomethionine), and stilbenes andderivatives thereof (e.g. stilbene oxide, trans-stilbene oxide).

[0056] Mixtures of antioxidants are likewise suitable for use in thecosmetic formulations according to the invention. Known and commercialmixtures are, for example, mixtures comprising, as active ingredients,lecithin, L-(+)-ascorbyl palmitate and citric acid (e.g. Oxynex® AP),natural tocopherols, L-(+)-ascorbyl palmitate, L-(+)-ascorbic acid andcitric acid (e.g. Oxynex® K LIQUID), tocopherol extracts from naturalsources, L-(+)-ascorbyl palmitate, L-(+)-ascorbic acid and citric acid(e.g. Oxynex® L LIQUID), DL-α-tocopherol, L-(+)-ascorbyl palmitate,citric acid and lecithin (e.g. Oxynex® LM) or butylhydroxytoluene (BHT),L-(+)-ascorbyl palmitate and citric acid (e.g. Oxynex® 2004).

[0057] The formulations according to the invention can also comprisevitamins as ingredients. Preferably, the vitamins used are vitamins andvitamin derivatives chosen from vitamin A, vitamin A propionate, vitaminA palmitate, vitamin A acetate, retinol, vitamin B, thiamine chloridehydrochloride (vitamin B₁), riboflavin (vitamin B₂) nicotinamide,vitamin C (ascorbic acid), vitamin D, ergocalciferol (vitamin D₂),vitamin E, DL-α-tocopherol, tocopherol E acetate, tocopherolhydrogensuccinate, vitamin K₁, esculin (vitamin P active ingredient),thiamine (vitamin B₁) nicotinic acid (niacin), pyridoxine, pyridoxal,pyridoaxmine, (vitamin B6), panthothenic acid, biotin, folic acid andcobalamine (vitamin B₁₂) are present in the cosmetic formulationsaccording to the invention, particularly preferably vitamin A palmitate,vitamin C, DL-α-tocopherol, tocopherol E acetate, nicotinic acid,panthothenic acid and biotin.

[0058] The compound according to the invention can be incorporated intocosmetic formulations in the customary manner. Suitable formulations arethose for external use, such as cream, lotion, gel or as a solutionwhich can be sprayed onto the skin. In this respect, it is preferred ifthe preparation comprises at least one oil phase and at least one waterphase, and that the 2-phenylbenzimidazolesulfonic acid according to theinvention is present in at least one aqueous phase.

[0059] The cosmetic or pharmaceutical formulations according to theinvention can take a number of terms, such as: solutions, suspensions,emulsions, PIT emulsions, pastes, ointments, gels, creams, lotions,powders, soaps, surfactant-containing cleansing preparations, oils,aerosols and sprays. Examples of other application forms are sticks,shampoos and shower preparations. Any customary carriers, auxiliariesand optionally further active ingredients may be added to theformulation.

[0060] Preferred auxiliaries originate from the group of preservatives,antioxidants, stabilizers, solubility promoters, vitamins, colorants,odour improvers.

[0061] Ointments, pastes, creams and gels may comprise the customarycarriers, e.g. animal and vegetable fats, waxes, paraffins, starch,tragacanth, cellulose derivatives, polyethylene glycols, silicones,bentonites, silica, talc and zinc oxide or mixtures of these substances.

[0062] Powders and sprays may comprise the customary carriers, e.g.lactose, talc, silica, aluminium hydroxide, calcium silicate andpolyamide powder or mixtures of these substances. Sprays canadditionally comprise customary propellants, e.g. chlorofluorocarbons,propane/butane or dimethyl ether.

[0063] Solutions and emulsions can comprise the customary carriers, suchas solvents, solubility promoters and emulsifiers, e.g. water, ethanol,isopropanol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzylbenzoate, propylene glycol, 1,3-butylglycol, oils, in particular cottonseed oil, peanut oil, wheatgerm oil, olive oil, castor oil and sesameoil, glycerol fatty acid ester, polyethylene glycols and fatty acidesters of sorbitan or mixtures of these substances.

[0064] Suspensions can comprise the customary carriers such as liquiddiluents, e.g. water, ethanol or propylene glycol, suspending agents,e.g. ethoxylated isostearyl alcohols, polyoxyethylene sorbitol estersand polyoxyethylene sorbitan esters, microcrystalline cellulose,aluminium metahydroxide, bentonite, agar agar and tragacanth or mixturesof these substances.

[0065] Soaps can comprise the customary carriers, such as alkali metalsalts of fatty acids, salts of fatty acid mono esters, fatty acidprotein hydrolysates, isethionates, lanolin, fatty alcohol, vegetableoils, plant extracts, glycerol, sugars or mixtures of these substances.

[0066] Surfactant-containing cleansing products can comprise thecustomary carrier substances, such as salts of fatty alcohol sulfates,fatty alcohol ether sulfates, sulfosuccinic monoesters, fatty acidprotein hydrolysates, isethionates, imidazolinium derivatives, methyltaurates, sarcosinates, fatty acid amide ether sulfates,alkylamidobetaines, fatty alcohols, fatty acid glycerides, fatty aciddiethanolamides, vegetable and synthetic oils, lanolin derivatives,ethoxylated glycerol fatty acid esters or mixtures of these substances.

[0067] Face and body oils can comprise the customary carrier substancessuch as synthetic oils, such as fatty acid esters, fatty alcohols,silicone oils, natural oils, such as vegetable oils and oily plantextracts, paraffin oils, lanolin oils or mixtures of these substances.

[0068] Cosmetic application forms also typical forms such as lipsticks,lip care sticks, mascara, eyeliner, eye shadow, blusher, powder makeup,emulsion make-up and wax make-up, and such protection products such assunscreen, pre-sun and after-sun preparations.

[0069] All compounds or components which can be used in the cosmeticformulations are either known and available commercially or can besynthesized by known processes.

[0070] The cosmetic formulation according to the invention isparticularly suitable for protecting human skin against the harmfulinfluences of the UV constituents in sunlight. It can also offerprotection to the skin against aging processes of the skin and againstoxidative stress, i.e. against damage caused by free radicals, as areproduced, for example, by solar irradiation, heat or other influences.In this connection, it is in various forms customarily used for thisapplication. For example, the formulation may be in the form of a lotionor emulsion, such as in the form of a cream or milk (O/W, W/O, O/W/O,W/O/W), in the form of oily-alcoholic, oily-aqueous or aqueous-alcoholicgels or solutions, in the form of solid sticks or may be formulated asan aerosol.

[0071] The formulation may comprise cosmetic auxiliaries which arecustomarily used in this type of preparation, such as thickeners,softeners, moisturizers, surface-active agents, emulsifiers,preservatives, antifoams, perfumes, waxes, lanolin, propellants, dyesand/or pigments which color the composition itself or the skin, andother ingredients customarily used in cosmetics.

[0072] It is possible to use an oil, wax or other fatty substance, alower monoalcohol or a lower polyol or mixtures thereof as a dispersantor solubilizer. Preferred monoalcohols or polyols include ethanol,isopropanol, propylene glycol, glycerol and sorbitol.

[0073] A preferred embodiment of the invention is an emulsion in theform of a protective cream or milk and which, apart from the2-phenylbenzimidazolesulfonic acid(s) according to the invention andpreferably further UV filters, comprise, for example, fatty alcohols,fatty acids, fatty acid esters, in particular triglycerides of fattyacids, lanolin, natural and synthetic oils or waxes and emulsifiers inthe presence of water.

[0074] Further preferred embodiments include oily lotions based onnatural or synthetic oils and waxes, lanolin, fatty acid esters, inparticular triglycerides of fatty acids, or oily-alcoholic lotions basedon a lower alcohol, such as ethanol, or a glycerol, such as propyleneglycol, and/or a polyol, such as glycerol, and oils, waxes and fattyacid esters, such as triglycerides of fatty acids.

[0075] The cosmetic preparation according to the invention can also bein the form of an alcoholic gel which comprises one or more loweralcohols or polyols, such as ethanol, propylene glycol or glycerol, anda thickener, such as siliceous earth. The oily-alcoholic gels alsocomprise natural or synthetic oil or wax.

[0076] The solid sticks consist of natural or synthetic waxes and oils,fatty alcohols, fatty acids, fatty acid esters, lanolin and other fattysubstances.

[0077] If a preparation is formulated as an aerosol, the customarypropellants, such as alkanes, fluoroalkanes and chlorofluoroalkanes areusually used.

[0078] The cosmetic formulation can also be used to protect the hairagainst photochemical damage in order to prevent changes of colorshades, decoloration or damage of a mechanical nature. In this case, asuitable formulation is in the form of a shampoo, lotion, gel oremulsion for rinsing out, the formulation in question being appliedbefore or after shampooing, before or after coloring or bleaching orbefore or after permanent waving. It is also possible to choose aformulation in the form of a lotion or gel for styling or treating thehair, in the form of a lotion or gel for brushing or blow-waving, in theform of a hair lacquer, permanent waving composition, colorant or bleachfor the hair. Apart from the 2-phenyl-benzimidazolesulfonic acid(s)according to the invention and further UV filters, the cosmeticformulation may comprise various adjuvants used in this type ofcomposition, such as surface-active agents, thickeners, polymers,softeners, preservatives, foam stabilizers, electrolytes, organicsolvents, silicone derivatives, oils, waxes, antigrease agents, dyesand/or pigments which color the composition itself or the hair, or otheringredients customarily used for hair care.

[0079] The cosmetic preparations according to the invention can beprepared using techniques which are well known to the person skilled inthe art.

[0080] To protect the skin and/or natural or sensitized hair againstsolar rays, a cosmetic preparation comprising the compound of theinvention is applied to the skin or the hair. Sensitized hair isunderstood here as meaning hair which has been subjected to a chemicaltreatment, such as a permanent waving treatment, a coloring process orbleaching process.

[0081] In addition, the compound of the invention also has a stabilizingeffect on the formulation. When used in corresponding products, theformulations are thus also stable for longer and do not change theirappearance. In particular, even in the case of longer-lastingapplication or relatively long storage, the effectiveness of theingredients, e.g. vitamins, is retained. This is particularlyadvantageous in the case of compositions for protecting the skin againstthe effect of UV rays since these cosmetics are exposed to particularlyhigh stresses by UV radiation.

[0082] The invention further provides for the stabilization ofparticular UV filters. A known high-performance class of lightprotection filter substances is formed by the dibenzoylmethanederivatives. However, a disadvantage is that these substances are veryreadily decomposed by UV light and thus their protecting properties arelost. An example of a light protection filter from this compound classwhich is available commercially is4-(tert-butyl)-4′-methoxydibenzoylmethane, which has the structure givenin formula IV. IV.

[0083] Surprisingly, it has now been found that the compound of theinvention has a very good stabilizing action for the dibenzoylmethanes,in particular 4-(tert-butyl)-4-methoxybenzoylmethane. By incorporatingmixtures of these compounds into cosmetics, it is now possible toprepare light protection compositions using dibenzoyl-methanes whichshow no or only a low decrease in the protective action against UV rays,even in the case of a relatively long period of solar action, forexample during sunbathing for a number of hours.

[0084] The entire disclosure of all applications, patents andpublications, cited above and below, and of corresponding GermanApplication No. 100 30 663.2, filed Jun. 23, 2000 is hereby incorporatedby reference.

[0085] The examples below illustrate the present invention in moredetail.

[0086] In the foregoing and in the following examples, all temperaturesare set forth uncorrected in degrees Celsium; and, unless otherwiseindicated, all parts and percentages are by weight.

[0087] Antaron® V-220 is sold by GAF, Frechen, DE,

[0088] Carbomer Ultrez-10 is supplied by Goodrich, Neuss, DE,

[0089] Dehymuls® E is a mixture of dicocoylpentaerythritol citrate,sorbitol sesquioleate, beeswax and aluminium stearate and is sold byCogni, Roermond, NL,

[0090] Eusolex® 2292, Eusolex® 232, Eusolex® 6300 and Eusolex®

[0091] HMS are UV filters sold by Merck KGaA, Darmstadt, DE,

[0092] Luvitol® EHO is sold by BASF AG, Ludwigshafen, DE,

[0093] Pemulen® TR-1 and Pemulen® TR-2 are acrylate/alkyl acrylatepolymers sold by Goodrich, Neuss, DE,

[0094] Performa V825 is a synthetic wax sold by New Phase, NJ08554, US,

[0095] Oxynex® K is a mixture of PEG-8, tocopherol, ascorbyl palmitate,ascorbic acid and citric acid and is sold by Merck KGaA, Darmstadt, DE.

EXAMPLE 1 Preparation of 2-phenylbenzimidazole-4,6-disulfonic Acid

[0096] 108 parts of o-phenylenediamine are introduced into 500 parts ofH₂SO₄ (>96%) and then 800 parts of oleum (65%) are added dropwise, thetemperature being maintained at a maximum of 120° C. After 15 min, themixture is cooled to 70° C. and 120 parts of benzoic acid are added. Themixture is heated for 2 h at 180° C. The mixture is slowly hydrolysedwith 2 500 parts of water, the temperature being maintained below 10° C.The precipitate (crystals) is filtered off with suction, the crudeproduct is suspended in 8 parts of water and dissolved with 32% sodiumhydroxide solution at pH =7. The solution is stirred with activatedcarbon until colorless, and thereafter precipitation is induced using96% H₂SO₄ by establishing a pH=1-2. 300 parts of2-phenylbenzimidazole-4,6-disulfonic acid are obtained. The compound hasan absorption maximum in the UV-B region at λ_(max)=308 nm.

[0097] The following are prepared analogously:

[0098] 2-(4′-methoxyphenyl)benzimidazole-4,6-disulfonic acid

[0099] 2-(3′-methoxyphenyl)benzimidazole-4,6-disulfonic acid

[0100] 2-(4′-ethoxyphenyl)benzimidazole-4,6-disulfonic acid

[0101] 2-(3′-ethoxyphenyl)benzimidazole-4,6-disulfonic acid

[0102] 2-(3′-5′-dimethoxyphenyl)benzimidazole-4,6-disulfonic acid

[0103] 2-(3′-5′-diethoxyphenyl)benzimidazole-4,6-disulfonic acid

[0104] 2-(3′-4′-diethoxyphenyl)benzimidazole-4,6-disulfonic acid.

EXAMPLE 2 Sunscreen Spray (O/W)

[0105] Phase Ingredient % by wt. A Eusolex ®2292 (Art. No. 105382) 7.50Eusolex ®HMS (Art. No. 111412) 7.00 Steareth-2 0.40 Steareth-10 0.80Pemulen ® TR-2 0.18 Propylene glycol isoceteth-3 acetate 5.00 Performa ®V 825 0.80 Dimethicone 1.00 Oxynex ®K (Art. No. 108324) 0.10 B2-Phenylbenzimidazole-4,6-disulfonic 1.00 acid Triethanolamine 0.901,2-Propanediol 2.00 Preservative 0.50 Water, demineralised ad 100.00

[0106] Preparation:

[0107] Phase B:

[0108] The water is mixed with the triethanolamine and the2-phenylbenzimidazole-4,6-disulfonic acid is added with stirring. Assoon as everything has dissolved, the other constituents of Phase B areadded and the mixture is heated to 80° C.

[0109] Phase A:

[0110] The constituents of Phase A, with the exception of Pemulen® TR-2,are combined and heated to 80° C. The Pemulen® TR-2 is added withstirring.

[0111] Preparation of the Sunscreen Composition:

[0112] Phase B is slowly added with stirring to Phase A. Followinghomogenization, the mixture is cooled with stirring. The preservativesused are 0.05% of propyl 4-hydroxybenzoate and 0.15% of methyl4-hydroxybenzoate.

EXAMPLE 3 Sunscreen Spray (O/W)

[0113] Phase Ingredient % by wt. A Eusolex ®2292 (Art. No. 105382) 7.50Eusolex ®HMS (Art. No. 111412) 7.00 Steareth-2 0.40 Steareth-10 0.80Pemulen ®TR-2 0.18 Propylene glycol isoceteth-3 acetate 5.00 Performa ®V825 0.80 Dimethicone 1.00 Oxynex ®K (Art. No. 108324) 0.10 B2-Phenylbenzimidazole-4,6-disulfonic 1.00 acid Eusolex ®232 (Art. No.105372) 1.00 Triethanolamine 0.90 1,2-Propanediol 2.00 Water,demineralized ad 100.00

[0114] Preparation:

[0115] Phase B:

[0116] The water is mixed with the triethanolamine and Eusolex® 232 andthe 2-phenylbenzimidazole-4,6-disulfonic acid are added with stirring.As soon as everything has dissolved, the other constituents of Phase Bare added and the mixture is heated to 80° C.

[0117] Phase A:

[0118] The constituents of Phase A, with the exception of Pemulen® TR-2,are combined and heated to 80° C. The Pemulen® TR-2 is added withstirring.

[0119] Preparation of the Sunscreen Composition:

[0120] Phase B is slowly added with stirring to Phase A. Afterhomogenization, the mixture is cooled with stirring. The preservativesused are 0.05% of propyl 4-hydroxybenzoate and 0.15% of methyl4-hydroxybenzoate.

EXAMPLE 4 Sunscreen Gel (Aqueous)

[0121] Phase Ingredient % by wt. A 2-Phenylbenzimidazole-4,6-disulfonic1.00 acid Eusolex ®232 (Art. No. 105372) 4.00 Sodium hydroxide solution6.00 Glycerol 3.00 1,2-Propanediol 2.00 Preservative q.s. Water,demineralized ad 100.00 B Carbomer Ultrez-10 0.70 Water, demineralized60.00 C Sodium hydroxide solution (10%) 1.50 Water, demineralized 4.00

[0122] Preparation:

[0123] Carbomer Ultrez-10 is completely dispersed in the water of PhaseB. Phase C is then slowly added and the mixture is homogenized.

[0124] For Phase A, the water is first added to the sodium hydroxidesolution. The Eusolex® 232 is added and completely dissolved withstirring. After a clear solution has been obtained, the otherconstituents of Phase A are added. Phase A is added in portions to themixture of Phases B and C, the mixture being homogenized after eachaddition.

[0125] The preservative used is:

[0126] 0.20% of methyl 4-hydroxybenzoate

EXAMPLE 5 Sunscreen Gel (O/W)

[0127] Phase Ingredient % by wt. A Eusolex ® 6300 (Art. No. 5385) 0.75Luvitol ® EHO 10.00  Dimethicone 2.00 Shea butter 5.00 Antaron ® V-2202.00 Oxynex ® K 1.00 B 2-Phenylbenzimidazole-4,6-disulfonic 1.00 acidEusolex ®232 (Art. No. 105372) 0.75 Tris(hydroxymethyl)aminomethane 0.33Preservative q.s. Water, demineralized 20.00  CTris(hydroxymethyl)aminomethane 1.20 Water, demineralized 10.00  DPemulen ® TR-1 0.60 Water, demineralized ad 100.00

[0128] Preparation:

[0129] The Pemulen® TR-1 is dissolved in the water of Phase D. Thetris(hydroxymethyl)aminomethane is dissolved in the water of Phase C andthe solution is added to Phase D. The tris(hydroxymethyl)aminomethane isdissolved in the water of Phase B and, with stirring, the Eusolex® 232is added. After a clear solution has been obtained, the otherconstituents of Phase B are added and Phase B is added to the mixture ofPhases C and D and homogenized. The constituents of Phase A are combinedand heated. Phase D is added to the mixture of the other phases withhomogenization.

[0130] The preservatives used are 0.05% of propyl 4-hydroxybenzoate and0.15% of methyl 4-hydroxybenzoate.

EXAMPLE 6 Sunscreen Gel (O/W)

[0131] Phase Ingredient % by wt. A Eusolex ® 6300 (Art. No. 5385) 0.75Luvitol ® EHO 10.00  Dimethicone 2.00 Shea butter 5.00 Antaron ® V-2202.00 Oxynex ® K liquid (Art. No. 8324) 1.00 B2-Phenylbenzimidazole-4,6-disulfonic 1.00 acid2,2′-(1,4-Phenylene)bis(1H- 0.75 benzimidazole-4,6-disulfonic acid)Tris(hydroxymethyl)aminomethane 0.33 Preservative q.s. Water,demineralized 20.00  C Tris(hydroxymethyl)aminomethane 1.20 Water,demineralized 10.00  D Pernulen ® TR-1 0.60 Water, demineralized ad100.00

[0132] Preparation:

[0133] The Pemulen® TR-1 is dissolved in the water of Phase D. Thetris(hydroxymethyl)aminomethane is dissolved in the water of Phase C andthe solution is added to Phase D. The tris(hydroxymethyl)aminomethane isdissolved in the water of Phase B and the2-phenylbenzimidazole-4,6-disulfonic acid and the2,2′-(1,4-phenylene)bis(1H-benzimidazole-4,6-disulfonic acid) is addedwith stirring. After a clear solution has been obtained, the otherconstituents of Phase B are added, and Phase B is added to the mixtureof Phases C and D and homogenized. The constituents of Phase A arecombined and heated. Phase A is added to the mixture of the other phaseswith homogenization.

[0134] The preservatives used are 0.05% of propyl 4-hydroxybenzoate and0.15% of methyl 4-hydroxybenzoate.

EXAMPLE 7 Sunscreen Lotion (W/O) with UVA/B Protection

[0135] Phase Ingredient % by wt. A Eusolex ® 2292 (Art. No. 105382) 3.00Eusolex ® 4360 (Art. No. 105376) 2.00 Dehymuls ® E 6.00 Hydrogenatedcastor oil 1.00 Beeswax 2.00 Oleyl erucate 6.00 Decyl oleate 6.00Dimethicone 1.00 Dicapryl ether 5.00 B Glycerol (87%) 5.002-Phenylbenzimidazole-4,6-disulfonic 3.00 acid Magnesium sulfateheptahydrate 1.00 Preservative q.s. Water, demineralized ad 100.00

[0136] Preparation:

[0137] The constituents of Phases A and B are each combined. Phase A isheated to 75° C. and Phase B is heated separately to 80° C. Phase B isadded to Phase A with homogenization. The mixture is cooled withstirring.

[0138] The preservatives used are:

[0139] 0.05% of propyl 4-hydroxybenzoate

[0140] 0.15% of methyl 4-hydroxybenzoate.

EXAMPLE 8 Sunscreen Lotion (W/O) with UVA/B Protection

[0141] Phase Ingredient % by wt. A Eusolex ® 2292 (Art. No. 105382) 3.00Eusolex ® 4360 (Art. No. 105376) 2.00 Dehymuls ® E 6.00 Hydrogenatedcastor oil 1.00 Beeswax 2.00 Oleyl erucate 6.00 Decyl oleate 6.00Dimethicone 1.00 Dicapryl ether 5.00 B2-Phenylbenzimidazole-4,6-disulfonic 2.00 acid2,2′-(1,4-Phenylene)bis(1H- 2.00 benzimidazole-5-sulfonic acid) Glycerol(87%) 5.00 Magnesium sulfate heptahydrate 1.00 Preservative q.s. Water,demineralized ad 100.00

[0142] Preparation:

[0143] The constituents of Phases A and B are each combined. Phase A isheated to 75° C. and, separately, Phase B is heated to 80° C. Phase B isadded to Phase A with homogenization. The mixture is cooled withstirring.

[0144] The preservatives used are:

[0145] 0.05% of propyl 4-hydroxybenzoate

[0146] 0.15% of methyl 4-hydroxybenzoate.

[0147] The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

[0148] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A 2-Phenylbenzimidazolesulfonic acid according to the formula I

wherein n is 0-2 and m is 2-3, R1, R2, R3, R4 and R5 each are a radicalselected from H, C₁₋₈-alkyl, C₁₋₈-alkoxy, hydroxyl, sulfate, nitro, F,Cl, Br or an I radical, and R6 is a C₁₋₈-alkyl or C₁₋₈-alkoxy radical.2. A 2-Phenylbenzimidazolesulfonic acid according to claim 1, whereinm=2 and n=0-1, and wherein at least 4 radicals from the group R1, R2,R3, R4 and R5 are H radicals.
 3. A process for the preparation of acompound according to claim 1, wherein an o-phenylenediamine accordingto formula II

is reacted with a compound according to the formula III

wherein R1, R2, R3, R4 and R5, are each, independently of one another, aradical selected from H, C₁₋₈-alkyl, C₁₋₈-alkoxy, hydroxyl, nitro, F,Cl, Br or an I radical, and wherein X is a radical selected from —COOH,—COCl, —COBr, —CN or —COOR, and wherein R is a C₁₋₂₀-alkyl radical.
 4. Amethod according to claim 3, wherein the reaction is carried out insulfuric acid.
 5. A UV filter substance comprised of a2-phenylbenzimidazolesulfonic acid according to claim
 1. 6. A cosmeticformulation having UV protection properties comprising at least onefilter substance comprised of at least one 2-phenylbenzimidazolesulfonicacid according to claim
 1. 7. A cosmetic formulation according to claim6, wherein the formulation comprises at least one oil phase and at leastone water phase, and wherein the 2-phenylbenzimidazolesulfonic acid ispresent in the at least one water phase.
 8. A cosmetic formulationaccording to claim 6, further comprising at least one additional UVfilter substance, wherein each filter substance is present in theformulation in an amount of from 0.5 to 20% by weight of the entireformulation.
 9. A cosmetic formulation according to claim 6, furthercomprising at least one of the following compounds3-(4′-methylbenzylidene)-dl-camphor,1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione,4-isopropyldibenzoylmethane, 2-hydroxy-4-methoxybenzophenone, octylmethoxycinnamate, 3,3,5-trimethylcyclohexyl salicylate, 2-ethylhexyl4-(dimethylamino)benzoate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylatecoated titanium dioxide, 2-phenylbenzimidazole-5-sulfonic acid and2,2′-(1,4-phenylene)bis(1H-benzimidazole-5-sulfonic acid).
 10. Astabilizing substance for a UV filter comprising a2-phenylbenzimidazolesulfonic acid according to claim
 1. 11. A methodaccording to claim 2, wherein the radicals R1-R5 are each an H radical.12. A method according to claim 3, wherein R is a C₁₋₈ alkyl radical.13. A method according to claim 4, wherein the sulphuric acid isactivated sulphuric acid.
 14. A method according to claim 4, wherein thereaction is carried out at a temperature of 160° C. to 190° C.
 15. Amethod according to claim 13, further comprising activating thesulphuric acid using chlorosulfonic acid or oleum.
 16. A methodaccording to claim 13, further comprising activating the sulphuric acidusing oleum.
 17. A UV filter substance according to claim 5, wherein theUV filter substance further comprises a UV-B filter substance.
 18. Aformulation according to claim 8, wherein the filter substance is a UV-Afilter substance.
 19. A formulation according to claim 8, wherein eachfilter substance is present in the formulation in an amount from 1 to15% by weight of the entire formulation.
 20. A formulation according toclaim 8, wherein each filter substance is presence in the formulation inan amount from 2 to 8% by weight of the entire formulation.
 21. Aformulation according to claim 8, wherein the filter substances togethercomprise from 5 to 25% by weight of the entire formulation.
 22. Aformulation according to claim 6, further comprising2-phenylbenzimidazole-5-sulfonic acid and/or2,2′-(1,4-phenylene)bis(1H-benzimidazole-5-sulfonic acid).
 23. Asubstance according to claim 10, wherein the UV filter isdibenzoylmethane or a derivative of dibenzoylmethane.
 24. A formulationaccording to claim 6, further comprising at least one antioxidant.
 25. Aformulation according to claim 6, further comprising at least onevitamin.